Many torrent clients has the ability to customize which columns are displayed for transfers, what I I'm looking for is the ability to sort by "Added" and "Completed" Timestamps. Thanks.

Click "Layout" -> "Select Columns..." to get them.

Ref: https://support.tixati.com/transfers%20view

How to configure columns: https://support.tixati.com/descriptions
It's a shame Tixati doesn't bring up that menu on a right-click which is standard behavior everywhere.